C++26: Trivial infinite loops are no longer undefined behaviour

Re:C++26: Trivial infinite loops are no longer undefined beh... by bryanlarsen on Friday September 18, 2026 @11:35AM (#49755909)

Probably by working together with Rust. Eliminating undefined behavior from unsafe Rust is a big deal for the Rust community at the moment. And given that most unsafe rust code exists to call into C or C++, concepts like pointer provenance need to be extended. And proper pointer provenance guarantees can both decrease UB and increase optimization potential.

IIUC, my understanding is shallow.

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Re:C++26: Trivial infinite loops are no longer undefined beh... by vlovich123 on Friday September 18, 2026 @12:18PM (#49756588)

That's a niche level thing that helps in some scenarios, and generally not as much for C++ which is much more weakly typed than Rust is. Weak typing + static typing is why safety problems in C++ are going to be really difficult to fix without fundamentally changing the language.

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Re:C++26: Trivial infinite loops are no longer undefined beh... by bryanlarsen on Friday September 18, 2026 @01:30PM (#49757556)

I expect some changes to the language from this direction, some way to attach provenance information or limitations to a pointer. Presumably through a #pragma at first. Strict typing in the C++ sense, not the Rust sense. An annotation like "volatile".

Pointer provenance is just one example, there are others.

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Re:C++26: Trivial infinite loops are no longer undefined beh... by nicoburns on Friday September 18, 2026 @11:37AM (#49755954)

This particular case is likely an example of that. Rust used to have this problem, but it wasn't ever intended to. So IIRC it got fixed in LLVM for Rust, and this is probably now C++ taking advantage of that.

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